Sailing,

If Delta can operate DC9's it can operate it's replacement, the E175. We are going to operate the 717. The numbers on the Next Gen CRJ-900 and E-195 are 15% better than the 717. So, obviously mainline can operate that airplane.

Perhaps your question is, "can mainline compete with GoJets?"

On a block hour basis the answer is probably no. Not unless we were willing to lower new hire pay to that of a comparable GoJets crew. This creates a very sticky political situation where junior pilots complain and senior pilots fear transfer of their flying to junior equipment.

Two things need to happen:
(1) ALPA needs to force management to look at costs beyond the block hour. ASA and Comair were a loss of 3.5 Billion Cap Ex, plus the strike, plus the loss on the fleet and capital improvements lavished on the subsidiaries (new HQ buildings, equipment, etc ...) Then there are the passenger handling costs associated with all of the mis connects, bumping, maintenance and staffing issues unique to having 8 different airlines with incompatible crews and maintenance. Triple redundant management structures, parasitic shareholders and litigation all adds up too.
(2) ALPA needs to educate union members on what a union is. Military pilots have not a clue (and have no reason to know) the history of the labor movement in our profession. For the most part, those from the top to the bottom of ALPA do not understand or appreciate "unity" as exclusive control over labor.

... and a third would be good:
(3) If you graph Delta's pay scales vs productivity, the large jet drivers are relatively underpaid compared to their small jet peers. The difference should be better understood so as to alleviate the fear 767 Captains have that somehow a Delta RJ pilot would harm their interests in future negotiations.